NSW Police said a light truck carrying oxy acetylene bottles of hydraulic fluid was travelling south on the Highway in Bergalia when the driver noticed flames coming from the rear of the vehicle.

The driver pulled over and dived from the vehicle before the cab was engulfed in flames.

Police said traffic was blocked in both directions until approximately 9pm due to the thick smoke and large fire.

Moruya Fire and Rescue captain Mark Gould said Crews from Moruya, Narooma, and Batemans Bay responded to the incident, while Rural Fire Service trucks were also in attendance.

"There's no hydrant out there, so we had the RFS crews doing water runs back and forth from Bergalia," he said. "They were basically rotating through, going to fill up before hooking back up to the pump.

"We're not sure of the cause of the fire yet, and the driver reported having minor burns. He didn't have time to grab his mobile phone or anything before he jumped out of the truck.

"It was a problem incident due to the highway closing, but we had to do it for people's safety. We couldn't let people drive past when there was the possibility of an explosion."

Mr Gould said firefighters had to concentrate on minimising that risk.

"There was one LPG cylinder that exploded, and the acetylene bottles had to be monitored," he said. "Acetylene can have a violent reaction if it gets too hot, so we had to keep it cool for a certain amount of time before we could transport it away.

"We did checks every 30 minutes to monitor temperature variations.

"There were also oils, diesels and grease on the truck, but they didn't give us any major issues."